Ventricular assist devices (“VAD”) are used to assist the heart of a patient suffering from heart failure. A VAD includes a pump having an inlet and an outlet. The pump is installed within the body of the patient, with the inlet of the pump communicating with a vein of the patient and with the outlet of the pump communicating with an artery. For example, where a VAD is used to assist the left ventricle of the heart, the inlet of the pump is in communication with the left ventricle, whereas the outlet is in communication with the aorta.
As described, for example, in U.S. Patent Application Publication No. 2009/0203957, the disclosure of which is hereby incorporated by reference herein, it has been proposed to mount a VAD with the housing of the pump disposed inside the heart. The pump may have an inlet at a proximal end of the housing and an outlet at a distal end of the housing. An outlet tube is connected to the distal end of the housing and projects through a valve of the heart into the appropriate artery. For example, where the VAD is used to assist the left ventricle, the outlet tube projects through the aortic valve into the aorta, so that the outlet of the pump is in communication with the aorta.
As described in the aforementioned patent publication, the housing of the pump may be connected by an elongated member to a proximal housing remote from the pump. Electrical connections extend through the elongated member from the proximal housing for connection to a controller and power source. In use, a device known as a sewing ring is fastened in place on the exterior of the heart. The sewing ring has a bore extending through it. The surgeon fastens the sewing ring in place on the exterior of the heart, typically at the apex of the heart. The surgeon makes a hole in the wall of the heart inside the bore of the sewing ring. The device is advanced through the bore and the hole in a distal direction, with the outlet tube and pump housing leading and with the proximal housing trailing.
The pump is advanced in this way until the pump is positioned with the outlet cannula projecting through the valve, and with the proximal housing disposed inside the sewing ring and projecting out of the exterior of the heart. A clamp associated with the sewing ring is then tightened so as to secure the proximal housing of the pump to the sewing ring, and thus fasten the pump in place in the heart. It is desirable to install such a pump without arresting the heart beat and without the use of a cardiopulmonary bypass machine. In such a procedure, commonly referred to as an “off-pump” procedure, the surgeon must form the hole and install the pump in the heart while the heart continues beating. As the heart beats, it tends to forcefully expel blood through the hole. Moreover, the pump should be introduced into the heart without also introducing a bolus of air into the interior of the heart. While a skillful surgeon can successfully perform an off-pump installation of such a pump without fatal blood loss or air embolism, further improvements would be desirable.